Changing tyres?

diamondbacker
diamondbacker Posts: 224
edited August 2013 in Road beginners
I've recently changed tyres on my road bike for Continental Touring Plus tyres these ( http://www.ribblecycles.co.uk/sp/road-t ... ONTTYRR205)

Since changing them I've noticed when I lift the bike at the seat and use my hand to pedal to make sure everything OK there is a bit of a wobble. The wheel is true and the tyre looks to be fitted fine and evenly all the way round. Is it normal for the wheel to have a slight wobble? Could the weight of the valve cause this?

Comments

  • dannyharris
    dannyharris Posts: 217
    Quick release tightened enough? Does the wheel have any play?
  • diamondbacker
    diamondbacker Posts: 224
    No, that doesn't seem to be it. To be honest I think the tyre might be dodgy as I've refitted it and tried a different tube but the same things happening. Might buy another tyre and give that a try later tomorrow.
  • smoggysteve
    smoggysteve Posts: 2,909
    It could be an illusion caused by the pattern of the tread. Sometimes it can make it look like its wobbling when its perfectly straight. Check it by spinning the wheel while looking at a reference point like a brake pad.
  • diamondbacker
    diamondbacker Posts: 224
    It actually feels like there is a weight on the wheel somewhere. It looks pretty straight but you can feel the frame shake/wobble with each revolution at a reasonable speed when I lift it.
  • smoggysteve
    smoggysteve Posts: 2,909
    would that not be the valve? do you us the valve screw nut? if so, try removing it. Its just dead weight that gets heavier as the wheel rotates faster.

    Also, to check wheels are seated correctly, undo the QR and thump the top of the tyre with your fist, this helps re seat it properly
  • CiB
    CiB Posts: 6,098
    Take the wheel out spin it on your thumbs, eyeballing the tyre wall against the rim. You might spot that it's not seated evenly somewhere on its circumference, in which case let it down to nearly flat and work your way round the full distance on both sides working it evenly into the rim. Push the valve up into the tyre to make sure the beads are properly located in the rim there too. Inflate it a bit and repeat the check, and inflate fully when satisfied that it's even.

    That said it is normal to get a bit of an imbalance when it's unloaded and spinning at speed. It doesn't matter in normal use.
  • Mickyg88
    Mickyg88 Posts: 289
    How much heavier does the valve screw nut get as the wheel rotates, is there a formula to calculate the weight per revolution, does it increase a hundred fold per 100 rpm, it would be really interesting to know how heavy an item weighing micro grams can get.
  • smoggysteve
    smoggysteve Posts: 2,909
    Have you ever had a car wheel balanced? A few grams can effect a wheel dramatically. If the wheel is feeling weighted in some way what else would you suggest before dismissing this?
  • Mickyg88
    Mickyg88 Posts: 289
    So you don't have a scientific answer, just an assumption, so how far do we go with this, shorten the valve stem? Come on smoggy...
  • andyeb
    andyeb Posts: 407
    Deflate the tyre, go round the edge checking the inner tube isn't caught underneath the tyre bead (the stiff ring which keeps the tyre on the wheel) and make sure the edge of the tyre is properly seated.

    If that doesn't fix it, try swapping the front and back tyres and/or rotating the tyre on the wheel by 90-180 degrees and try again.
  • smoggysteve
    smoggysteve Posts: 2,909
    Mickyg88 wrote:
    So you don't have a scientific answer, just an assumption, so how far do we go with this, shorten the valve stem? Come on smoggy...

    Well after riding bikes for over 2 decades I think I understand the physics of it. When you get a light wheel and lift it up and spin it, at a high speed almost all with have a slight wobble caused by the weight of the valve and parts attached. When it settles, especially on a light rim the valve will settle at the bottom. Now, if the rest of the wheel shows no sign of buckling or deformation then common sense and the process of elimination leaves just the valve. Sure most scientific conclusions use a similar process.
  • gozzy
    gozzy Posts: 640
    OP, do you still have the old tyre? Have you tried putting it back on and seeing if the same effect occurs? Tried swapping front and rear tyres out?
  • diamondbacker
    diamondbacker Posts: 224
    Yes, just put a brand new tyre on and the wheel is no longer wobbling. I'm 99% sure that the tyre I was trying to put on originally was faulty. Shame I spent a good chunk of the morning fitting and refitting the other tyre to try and get it not to wobble.

    Could have been worse I guess if the wheel was faulty.

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